Buggy code:
public class PacketConfigSync implements IMessageHandler < PacketConfigSync . ConfigSyncMessage , IMessage > { @ Override public IMessage onMessage ( PacketConfigSync . ConfigSyncMessage message , MessageContext context ) { } public static class ConfigSyncMessage implements IMessage { public ConfigSyncMessage ( ) { } @ Override public void toBytes ( ByteBuf dataStream ) { } @ Override public void fromBytes ( ByteBuf dataStream ) { general . updateNotifications = dataStream . readBoolean ( ) ; general . controlCircuitOreDict = dataStream . readBoolean ( ) ; general . logPackets = dataStream . readBoolean ( ) ; general . dynamicTankEasterEgg = dataStream . readBoolean ( ) ; general . voiceServerEnabled = dataStream . readBoolean ( ) ; general . cardboardSpawners = dataStream . readBoolean ( ) ; general . creativeOverrideElectricChest = dataStream . readBoolean ( ) ; general . spawnBabySkeletons = dataStream . readBoolean ( ) ; general . obsidianTNTDelay = dataStream . readInt ( ) ; general . obsidianTNTBlastRadius = dataStream . readInt ( ) ; general . UPDATE_DELAY = dataStream . readInt ( ) ; general . FROM_IC2 = dataStream . readDouble ( ) ; general . TO_IC2 = dataStream . readDouble ( ) ; general . FROM_TE = dataStream . readDouble ( ) ; general . TO_TE = dataStream . readDouble ( ) ; general . FROM_H2 = dataStream . readDouble ( ) ; general . ETHENE_BURN_TIME = dataStream . readInt ( ) ; general . ENERGY_PER_REDSTONE = dataStream . readDouble ( ) ; general . DISASSEMBLER_USAGE = dataStream . readDouble ( ) ; general . VOICE_PORT = dataStream . readInt ( ) ; general . maxUpgradeMultiplier = dataStream . readInt ( ) ; general . activeType = EnergyType . values ( ) [ dataStream . readInt ( ) ] ; general . minerSilkMultiplier = dataStream . readDouble ( ) ; general . blacklistIC2 = dataStream . readBoolean ( ) ; general . blacklistRF = dataStream . readBoolean ( ) ; for ( MachineType type : MachineType . getValidMachines ( ) ) { machines . setEntry ( type , dataStream . readBoolean ( ) ) ; } usage . enrichmentChamberUsage = dataStream . readDouble ( ) ; usage . osmiumCompressorUsage = dataStream . readDouble ( ) ; usage . combinerUsage = dataStream . readDouble ( ) ; usage . crusherUsage = dataStream . readDouble ( ) ; usage . factoryUsage = dataStream . readDouble ( ) ; usage . metallurgicInfuserUsage = dataStream . readDouble ( ) ; usage . purificationChamberUsage = dataStream . readDouble ( ) ; usage . energizedSmelterUsage = dataStream . readDouble ( ) ; usage . digitalMinerUsage = dataStream . readDouble ( ) ; usage . electricPumpUsage = dataStream . readDouble ( ) ; usage . rotaryCondensentratorUsage = dataStream . readDouble ( ) ; usage . oxidationChamberUsage = dataStream . readDouble ( ) ; usage . chemicalInfuserUsage = dataStream . readDouble ( ) ; usage . chemicalInjectionChamberUsage = dataStream . readDouble ( ) ; usage . precisionSawmillUsage = dataStream . readDouble ( ) ; usage . chemicalDissolutionChamberUsage = dataStream . readDouble ( ) ; usage . chemicalWasherUsage = dataStream . readDouble ( ) ; usage . chemicalCrystallizerUsage = dataStream . readDouble ( ) ; usage . seismicVibratorUsage = dataStream . readDouble ( ) ; usage . fluidicPlenisherUsage = dataStream . readDouble ( ) ; usage . gasCentrifugeUsage = dataStream . readDouble ( ) ; usage . heavyWaterElectrolysisUsage = dataStream . readDouble ( ) ; try { for ( IModule module : Mekanism . modulesLoaded ) { module . readConfig ( dataStream ) ; } } catch ( Exception e ) { e . printStackTrace ( ) ; } <START_BUG> proxy . onConfigSync ( ) ; <END_BUG> } } }

Fix:
proxy . onConfigSync ( true ) ;